Few issues in American history are as likely to cause knee-jerk reactions as the Vietnam War. Some see it as an immoral and unpopular conflict; others argue that it was winnable but that our military tactics were misguided. Flynn's ( North to Yesterday ) fifth novel doesn't try to pick its way through this minefield of opinion, but instead sets off as many tripwires as it can. Sherrill O'Connell, struggling novelist and professor at a small Texas college, tries to escape the memories of his 13-year-old daughter's death by convincing a right-wing magazine named REAL to employ him as their Vietnam war correspondent. When O'Connell is caught in a small battle in which his life and those of a TV crew are endangered, he picks up a fallen soldier's rifle and kills three Viet Cong. The media turn him into an instant celebrity--a blood-and-guts monster who bears little resemblance to the mildly conservative O'Connell. Having been exploited by the editors at REAL , O'Connell is then accused of participating in a massacre of civilians. He finds himself in a maze of falsehoods, unable to change his tough image without risking his credibility. His dilemma, told clearly and simply, raises disturbing questions about perception and truth, loyalty and betrayal. Flynn, a former Marine and Vietnam correspondent, proves himself as thoroughly familiar with the human condition as he is with the military (``klick'' is an Army term meaning ``kilometer''). Author tour. (Mar.)